Re: [PATCH] drm/msm/adreno: fix userspace-triggered crash on a2xx-a4xx

[Rob Clark <rob.clark@oss.qualcomm.com>]

On Mon, Apr 6, 2026 at 3:14 PM Dmitry Baryshkov
<dmitry.baryshkov@oss.qualcomm.com> wrote:
>
> Before a5xx Adreno driver will not try fetching UBWC params (because
> those generations didn't support UBWC anyway), however it's still
> possible to query UBWC-related params from the userspace, triggering
> possible NULL pointer dereference. Check for UBWC config in
> adreno_get_param() and return sane defaults if there is none.
>
> Fixes: a452510aad53 ("drm/msm/adreno: Switch to the common UBWC config struct")
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> ---
>  drivers/gpu/drm/msm/adreno/adreno_gpu.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> index d5fe6f6f0dec..7dc95c0a17f7 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> @@ -426,16 +426,25 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_context *ctx,
>                 *value = vm->mm_range;
>                 return 0;
>         case MSM_PARAM_HIGHEST_BANK_BIT:
> -               *value = adreno_gpu->ubwc_config->highest_bank_bit;
> +               if (!adreno_gpu->ubwc_config)
> +                       *value = 13;
> +               else
> +                       *value = adreno_gpu->ubwc_config->highest_bank_bit;

These three params are only used by userspace on a6xx, so tbh it would
be ok to return -ENOENT for platforms that have no ubwc config.  That
might be better than returning imaginary values.

BR,
-R

>                 return 0;
>         case MSM_PARAM_RAYTRACING:
>                 *value = adreno_gpu->has_ray_tracing;
>                 return 0;
>         case MSM_PARAM_UBWC_SWIZZLE:
> -               *value = adreno_gpu->ubwc_config->ubwc_swizzle;
> +               if (!adreno_gpu->ubwc_config)
> +                       *value = 0;
> +               else
> +                       *value = adreno_gpu->ubwc_config->ubwc_swizzle;
>                 return 0;
>         case MSM_PARAM_MACROTILE_MODE:
> -               *value = adreno_gpu->ubwc_config->macrotile_mode;
> +               if (!adreno_gpu->ubwc_config)
> +                       *value = 0;
> +               else
> +                       *value = adreno_gpu->ubwc_config->macrotile_mode;
>                 return 0;
>         case MSM_PARAM_UCHE_TRAP_BASE:
>                 *value = adreno_gpu->uche_trap_base;
>
> ---
> base-commit: 36ece9697e89016181e5ae87510e40fb31d86f2b
> change-id: 20260407-adreno-fix-ubwc-6a2564710e21
>
> Best regards,
> --
> With best wishes
> Dmitry
>